In this segment, Part 5, we will create a VMware Virtual Center (vCenter) virtual machine and place the ESX and ESXi machines under management. Using this vCenter instance, we will complete the configuration of ESX and ESXi using some of the new features available in vCenter.

Part 5, Managing our ESX Cluster-in-a-Box

With our VSA and ESX servers purring along in the virtual lab, the only thing stopping us from moving forward with vMotion is the absence of a working vCenter to control the process. Once we have vCenter installed, we have 60-days to evaluate and test vSphere before the trial license expires.

Prepping for vCenter Server for vSphere

We are going to install Microsoft Windows Server 2003 STD for the vCenter Server operating system. We chose Server 2003 STD since we have limited CPU and memory resources to commit to the management of the lab and because our vCenter has no need of 64-bit resources in this use case.

Since one of our goals is to have a fully functional vMotion lab with reasonable performance, we want to create a vCenter virtual machine with at least the minimum requirements satisfied. In our 24GB lab server, we have committed 20GB to ESX, ESXi and the VSA (8GB, 8GB and 4GB, respectively). Our base ESXi instance consumes 2GB, leaving only 2GB for vCenter – or does it?

Memory Use in ESXi

VMware ESX (and ESXi) does a good job of conserving resources by limiting commitments for memory and CPU. This is not unlike any virtual memory capable system that puts a premium on “real” memory by moving less frequently used pages to disk. With a lot of idle virtual machines, this ability alone can create significant over-subscription possibilities for VMware; this is why it could be possible to run 32GB worth of VM’s to run on a 16-24GB host.

Do we really want this memory paging to take place? The answer – for the consolidation use cases – is usually “yes.” This is because consolidation is born out of the need to aggregate underutilized systems in a more resource efficient way. Put another way, administrators tend to provision systems based on worst case versus average use, leaving 70-80% of those resources idle in off-peak times. Under ESX’s control those underutilized resources can be re-tasked to another VM without impacting the performance of either one.

On the other hand, our ESX and VSA virtual machines are not the typical use case. We intend to fully utilized their resources and let them determine how to share them in turn. Imagine a good number of virtual machines running on our virtualized ESX hosts: will they perform well with the added hardship of memory paging? Also, when begin to use vMotion those CPU and memory resources will appear on BOTH virtualized ESX servers at the same time.

It is pretty clear that if all of our lab storage is committed to the VSA, we do not want to page its memory. Remember that any additional memory not in use by the SAN OS in our VSA is employed as ARC cache for ZFS to increase read performance. Paging memory that is assumed to be “high performance” by NexentaStor would result in poor storage throughput. The key to “recursive computing” is knowing how to anticipate resource bottlenecks and deploy around them.

This brings the question: how much memory is left after reserving 4GB for the VSA? To figure that out, let’s look at what NexentaStor uses at idle with 4GB provisioned:

NexentaStor's RAM footprint with 4GB provisioned, at idle.

As you can see, we have specified a 4GB reservation which appears as “4233 MB” of Host Memory consumed (4096MB+137MB). Looking at the “Active” memory we see that – at idle – the NexentaStor is using about 2GB of host RAM for OS and to support the couple of file systems mounted on the host ESXi server (recursively).

Additionally, we need to remember that each VM has a memory overhead to consider that increases with the vCPU count. For the four vCPU ESX/ESXi servers, the overhead is about 220MB each; the NexentaStor VSA consumes an additional 140MB with its two vCPU’s. Totaling-up the memory plus overhead identifies a commitment of at least 21,828MB of memory to run the VSA and both ESX guests – that leaves a little under 1.5GB for vCenter if we used a 100% reservation model.

Memory Over Commitment

The same concerns about memory hold true for our ESX and ESXi hosts – albeit in a less obvious way. We obviously want to “reserve” memory for required by the VMM – about 2.8GB and 2GB for ESX and ESXi respectively. Additionally, we want to avoid over subscription of memory on the host ESXi instance – if at all possible – since it will already be working running our virtual ESX and ESXi machines.

In this segment, Part 4, we will create an ESXi instance on NFS along with an ESX instance on iSCSI, and, using writable snapshots, turn both of these installations into quick-deploy templates. We’ll then mount our large iSCSI target (created in Part 3) and NFS-based ISO images to all ESX/ESXi hosts (physical and virtual), and get ready to install our vCenter virtual machine.

Part 4, Making an ESX Cluster-in-a-Box

With a lot of things behind us in Parts 1 through 3, we are going to pick-up the pace a bit. Although ZFS snapshots are immediately available in a hidden “.zfs” folder for each snapshotted file system, we are going to use cloning and mount the cloned file systems instead.

Cloning allows us to re-use a file system as a template for a copy-on-write variant of the source. By using the clone instead of the original, we can conserve storage because only the differences between the two file systems (the clone and the source) are stored to disk. This process allows us to save time as well, leveraging “clean installations” as starting points (templates) along with their associate storage (much like VMware’s linked-clone technology for VDI.) While VMware’s “template” capability allows us save time by using a VM as a “starting point” it does so by copying storage, not cloning it, and therefore conserves no storage.

Using clones in NexentaStor to conserve storage and aid rapid deployment and testing. Only the differences between the source and the clone require additional storage on the NexentaStor appliance.

While the ESX and ESXi use cases might not seem the “perfect candidates” for cloning in a “production” environment, in the lab it allows for an abundance of possibilities in regression and isolation testing. In production you might find that NFS and iSCSI boot capabilities could make cloned hosts just as effective for deployment and backup as they are in the lab (but that’s another blog).

Here’s the process we will continue with for this part in the lab series:

Create NFS folder in NexentaStor for the ESXi template and share via NFS;

Modify the NFS folder properties in NexentaStor to:

limit access to the hardware ESXi host only;

grant the hardware ESXi host “root” access;

Create a folder in NexentaStor for the ESX template and create a Zvol;

From VI Client’s “Add Storage…” function, we’ll add the new NFS and iSCSI volumes to the Datastore;

Create ESX and ESXi clean installations in these “template” volumes as a cloning source;

Unmount the “template” volumes using the VI Client and unshare them in NexentaStore;

Clone the “template” Zvol and NFS file systems using NexentaStore;

Mount the clones with VI Client and complete the ESX and ESXi installations;

Mount the main Zvol and ISO storage to ESX and ESXi as primary shared storage;

There are many features in vSphere worth exploring but to do so requires committing time, effort, testing, training and hardware resources. In this feature, we’ll investigate a way – using your existing VMware facilities – to reduce the time, effort and hardware needed to test and train-up on vSphere’s ESXi, ESX and vCenter components. We’ll start with a single hardware server running VMware ESXi free as the “lab mule” and install everything we need on top of that system.

Part 1, Getting Started

To get started, here are the major hardware and software items you will need to follow along:

Recommended Lab Hardware Components

One 2P, 6-core AMD “Istanbul” Opteron system

Two 500-1,500GB Hard Drives

24GB DDR2/800 Memory

Four 1Gbps Ethernet Ports (4×1, 2×2 or 1×4)

One 4GB SanDisk “Cruiser” USB Flash Drive

Either of the following:

One CD-ROM with VMware-VMvisor-Installer-4.0.0-164009.x86_64.iso burned to it

An IP/KVM management card to export ISO images to the lab system from the network

For the hardware items to work, you’ll need to check your system components against the VMware HCL and community supported hardware lists. For best results, always disable (in BIOS) or physically remove all unsupported or unused hardware- this includes communication ports, USB, software RAID, etc. Doing so will reduce potential hardware conflicts from unsupported devices.

The Lab Setup

We’re first going to install VMware ESXi 4.0 on the “test mule” and configure the local storage for maximum use. Next, we’ll create three (3) machines two create our “virtual testing lab” – deploying ESX, ESXi and NexentaStor running directly on top of our ESXi “test mule.” All subsequent tests VMs will be running in either of the virtualized ESX platforms from shared storage provided by the NexentaStor VSA.

In Medio Stat Veritas

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